% 采样点和权重, Gauss 7
pos = [
    1/3, 1/3;
    0.5, 0.5;
    0, 0.5;
    0.5, 0;
    1, 0;
    0, 1;
    0, 0];
coe = [
    0.45...
    0.13333333,0.13333333,0.13333333 ...
    0.05,0.05,0.05];